Comparison of memory effect between YMnO3 and SrBi2Ta2O9 ferroelectric thin films deposited on Si substrates

For the ferroelectric gate-type capacitors, we have fabricated ${\mathrm{Pt/YMnO}}_{\mathrm{3}}\mathrm{(YMO)/Si}$ and ${\mathrm{Pt/SrBi}}_{\mathrm{2}}{\mathrm{Ta}}_{\mathrm{2}}{\mathrm{O}}_{\mathrm{9}}\mathrm{(SBT)/Si}$ structures. We have used the highly $c$ -axis oriented hexagonal YMO thin films ${\mathrm{(\epsilon }}_r\text{≈19)}$ and the polycrystalline SBT thin films ${\mathrm{(\epsilon }}_r\text{≈150)}$ with a dominant (115) orientation, respectively. The memory effect resulting from the ferroelectric switching properties is investigated as a function of the dielectric constant of ferroelectric thin films with 150 nm in thickness. About 3 times wider memory window is obtained by using a relatively low dielectric constant of YMO than that using a relatively high dielectric constant of SBT. Typical memory windows of the Pt/YMO/Si and the Pt/SBT/Si capacitors are 1.24 and 0.34 V, respectively, at a gate voltage of 5 V.